In a note to clients on Thursday on "the $1 trillion flow that
conquers all," Hartnett observed that the amount of financial
assets added to central banks' balance sheets is the "one flow
that matters" in the market.

Put another way, the $1 trillion in bonds and stocks bought since
the start of 2017 by central banks like the ECB, BOJ, Swiss
National Bank puts purchases on pace for $3.6 trillion in buying
this year, the highest dating back to the start of the global
financial crisis in 2007.

Hartnett argues this big increase in central bank balance sheets
has held down bond yields and supported stock prices. So, even
with rising geopolitical uncertainty that one would think might
put a dent in markets, there has been relative stability in
Hartnett's eyes.